Diversion or theft of cargo that is being transported by a land, water-borne or air-borne vehicle is still big business. One estimate of the value of cargo that is stolen from land, sea and air vehicles annually is tens of billions of dollars. In some instances, the vehicle and its cargo are diverted, until the cargo can be removed from the vehicle in an undisclosed location, safe from the inquisitive eyes and ears of law enforcement officials. In other instances, the cargo is promptly off-loaded from the original transport vehicle and is either stored at an undisclosed location for some period of time or is immediately transported to one or more other locations for disposal or for some purpose. After the stolen cargo has been missing for at least 8-24 hours, the likelihood of cargo recovery drops dramatically, except for certain unique and easily distinguishable items such as atomic energy fuel and well known art objects. At the same time, it is often difficult to keep track of the location of the original cargo transport vehicle and or to determine whether any portion of the cargo has been off-loaded for storage at, or movement to, an undisclosed location.
Mobile unit tracking, for location of a missing vehicle or person, for monitoring vehicle progress along a given route, for determination that an emergency has occurred, or for similar purposes, is disclosed in U.S. Pat. Nos. 4,651,157 and 5,003,317, issued to Gray et al, U.S. Pat. Nos. 4,818,908 and 4,908,629, issued to Apsell et al, U.S. Pat. Nos. 4,891,650, 5,055,851, 5,131,019 and 5,218,367, issued to Sheffer et al, U.S. Pat. No. 4,905,271, issued to Namekawa, U.S. Pat. No. 5,014,206, issued to Scribner et al, U.S. Pat. No. 5,115,224, issued to Kostusiak, U.S. Pat. No. 5,208,756, issued to Song, U.S. Pat. No. 5,223,844, issued to Mansell et al, U.S. Pat. Nos. 5,225,224 and 5,379,224, issued to Brown et al, U.S. Pat. No. 5,289,163, issued to Perez et al, U.S. Pat. No. 5,293,642, issued to Lo, U.S. Pat. No. 5,347,274, issued to Hassett, U.S. Pat. No. 5,374,936, issued to Feng, U.S. Pat. No. 5,398,190, issued to Wortham, U.S. Pat. No. 5,422,813, issued to Schuchman et al. These patents are incorporated by reference herein.
Cargo security systems, often involving provision of physical resistance or other dissuasion methods to an unauthorized cargo off-loader or cargo diverter, are disclosed in U.S. Pat. No. 3,961,323, issued to Hartkorn, U.S. Pat. No. 4,035,765, issued to Wenner et al, U.S. Pat. No. 4,543,983, issued to Murray, U.S. Pat. No. 4,742,357, Issued to Rackley, U.S. Pat. No. 4,750,197, issued to Denekamp et al, U.S. Pat. No. 4,844,305, issued to McKneely, U.S. Pat. Nos. 4,897,642 and 5,025,253, issued to DiLullo et al, U.S. Pat. No. 4,908,606, issued to Kevonian, U.S. Pat. No. 5,005,664, issued to Harris et al, and U.S. Pat. No. 5,081,667, issued to Drori et al. These patents are incorporated by reference herein.
Use of measured signal strength to estimate the distance of a mobile unit from a plurality fixed transmitters or receivers is disclosed in U.S. Pat. Nos. 4,891,650, 5,055,851 and 5,218,367, issued to Sheffer et al, in U.S. Pat. No. 5,289,163, issued to Perez et al, and in U.S. Pat. No. 5,374,936, issued to Feng. These patents are incorporated by reference herein.
The approaches disclosed in these patents focus on tracking a vehicle for the purpose of resisting off-loading or diversion of cargo from a vehicle, not on integrated tracking and protection of a vehicle and its cargo.
What is needed is an enhanced location determination system that (1) tracks the location of the vehicle and of the cargo relative to the vehicle, (2) reports any out-of-the-ordinary lapses in receipt of signals sufficient to determine the vehicle present location and/or cargo present location, (3) determines when some portion of the cargo is being or has been off-loaded at other than an approved location, (4) determines when the vehicle is within a signal-obstructing region, (5) determines when a vehicle is within a selected travel corridor, (6) determines when the vehicle velocity has been abnormally low for too long a time, and/or (7) transmits an alarm signal, including the last-known location of the vehicle and/or the cargo, if some abnormal event is determined to have occurred. Preferably, this system should have the capabilities of tracking the location of the vehicle and of sensing movement of the cargo independently and should provide substantial flexibility in determining and reporting whether an abnormal event has occurred or is occurring and the type of abnormal event.